Phosphorus-containing flame retardants

ABSTRACT

A flame-retardant resin composition comprises a base resin (A), such as a polyamide resin, and an aromatic organophosphorus oligomer or polymer.

This application is a continuation in part of U.S. patent applicationSer. No. 12/776,593, filed May 10, 2010 and which claims the benefit ofthe filing date of U.S. Provisional Application No. 61/177,750 filed May13, 2009, the entire contents of each disclosure are incorporated hereinby reference.

FIELD

This invention relates to phosphorus-containing flame retardantsparticularly, but not exclusively for glass-filled polyamide resins.

BACKGROUND

With current and future market requirements for electrical componentstrending toward lighter weight plastic parts with improved electricaland mechanical properties, there is a substantial growth in the use ofengineering plastics for electronic applications. At the present time,polyamides are the dominant engineering thermoplastic for electronic andother applications, especially when reinforced with a glass filler toincrease their structural and impact strength and rigidity.

Polyamides are, in general, characterized as being relatively thermallystable upon long exposure to processing temperatures and shear. Uponexposure to flame, however, they burn quite readily, with theflammability being characterized by a dripping behavior of the burningresin. There is therefore a substantial and increasing demand for flameretardant polyamides and especially flame retardant glass-filledpolyamides. Likewise, there is also demand for their polyester resincousins, typically glass reinforced, with the choice of resin beingdependent on several factors such as a balance between cost andmechanical property performance.

One of the major classes of flame retardants for thermoplastics andpolyurethane foams is that of organic phosphorus compounds (typicallyphosphates and phosphonates). These may be non-halogenated or mayinclude phosphorus-halogen compounds and blends of phosphorous compoundswith halogenated flame retardants, typically brominated flameretardants.

In general organic phosphorus compounds provide fire retardant activitythrough a combination of condensed phase reactions, vapor phasereactions, polymer carbonization promotion, and/or char formation. Theseprocesses obviously depend on the polymer in which such additive(s)reside. Therefore, specific phosphorus containing structures need to bedesigned for various polymers types.

For example, U.S. Pat. No. 3,681,281 discloses a shaped structurecomprising a polyester, at least 1 percent by weight of the polyester ofa tertiary phosphine oxide, and from about 10 to about 50 percent byweight of the tertiary phosphine oxide of a synergist selected from thegroup consisting of triphenylmelamine, benzil and dibenzyl. Among thetertiary phosphine oxides exemplified is xylylene bis-diphenylphosphineoxide.

In an article entitled “Phosphorus based additives for flame retardantpolyester. 1. Low molecular weight additives”, Industrial & EngineeringChemistry Product Research and Development, (1982), 21(2), pages 328-31,Robert W Stackman evaluates various phosphorus-containing organiccompounds, including xylylene bis-diphenylphosphine oxide, as flameretardants for poly(ethylene terephthalate) and poly(1,4-butyleneterephthalate). The evaluation includes the effect of the additives onmelt stability of preformed polymers as well as the effect uponflammability of films, as determined by a non-standard bottom burn,oxygen index method. The oxygen index values for these blends were afunction of the phosphorus content of the blend. The efficiency of thephosphorus compounds as flame retardants changed as the nature of thephosphorus structure changed, with the order R3PO>R(R′O)2PO>(R′O)3PO.Polymeric additives were reported to be attractive additives, giving acombination of a high degree of flame retardancy combined with a minordegree of property degradation on blending, even at <20 wt % of theblend.

Other organic phosphorus compounds have also been suggested for use asflame retardants for polyamides. For example, Research Disclosure 168051(published April 1978) entitled “Improved Nylon” describes aflame-resistant nylon fiber prepared by coating flakes ofbis(4-aminocyclohexyl)methane-dodecanedioic acid copolymer with 8-10%p-xylylenebis(diphenylphosphine oxide) flame retardant and spinning ayarn using a screw melter equipped with a homogenizing, in-line mixer tosupply the molten polymer to a unit for producing a 34-filament yarn.The molten polymer was heated to 300-10° and the holdup time wasapproximately 15 min. The yarn was drawn 2.3 times on a hot pipe toproduce a 100-denier yarn.

In addition, U.S. Pat. No. 4,341,696 discloses a glass filledthermoplastic polyamide polymer rendered flame retardant by havingcombined therewith an effective amount of atris-(3-hydroxyalkyl)phosphine oxide having the formula:

wherein R₁ and R₃ are any radical selected from the group consisting ofhydrogen, phenyl and alkyl radicals of 1 to 4 carbon atoms and R2 is anyradical selected from the group consisting of hydrogen, phenyl and alkylradicals of 2 to 4 carbon atoms, provided that when R₁ and R₃ arehydrogen radicals, R2 is either an alkyl radical of 2 to 4 carbon atomsor a phenyl radical.

U.S. Pat. No. 7,332,534 discloses a flame retardant formulation forthermoplastic and thermoset polymers, including polyesters andpolyamides, containing, as flame retardant component A, from 90 to 99.9%by weight of phosphinate salt of the formula:

and/or a diphosphinate salt of the formula

and/or polymers thereof, where R1, R2 are the same or different and areeach C1-C6-alkyl, linear or branched, and/or aryl; R3 isC1-C10-alkylene, linear or branched, C6-C10-arylene, -alkylarylene or-arylalkylene; M is Mg, Ca, Al, Sb, Sn, Ge, Ti, Zn, Fe, Zr, Ce, Bi, Sr,Mn, Li, Na and/or K; m is from 1 to 4; n is from 1 to 4; x is from 1 to4 and, as component B, from 0 to 50% by weight of a nitrogen-containingsynergist or of a phosphorus/nitrogen flame retardant and, as componentC, from 0.1 to 10% by weight of a liquid component.

U.S. Pat. No. 7,411,013 discloses a flame-retardant resin compositioncomprising a base resin (A), such as a polyester, polyamide or styrenicresin, an organic phosphorus compound (B) and a flame-retardantauxiliary (C), wherein the organic phosphorus compound (B) has a unitrepresented by the following formula:

wherein Ar represents an aromatic hydrocarbon ring or anitrogen-containing aromatic heterocycle; X1 represents an oxygen atomor a sulfur atom; Y1 and Y2 are the same or different and eachrepresents a hydrocarbon group, an alkoxy group, an aryloxy group, or anaralkyloxy group; Z1 represents an alkylene group, or anitrogen-containing bivalent group corresponding to an alkylamine; Y1and Y2 may bind to each other, and Y1 and Y2 together with the adjacentphosphorus atom may form a ring; “a” denotes 0 or 1; and “b” denotes aninteger of 1 to 6.

According to the present invention, it has now been found that certainbenzyl-substituted phosphorus oxide compounds, especially when combinedwith specific synergists, are highly effective flame retardants forthermoplastic resins, including polyamides, especially glass filledpolyamides.

SUMMARY

Accordingly, the invention resides in one aspect in a flame-retardantresin composition comprising a base resin (A), an organophosphoruscompound (B) comprising a unit represented by at least one of thefollowing formulas (I), (Ia), (II) and (III):

where A is selected from O, S, SO₂, a single bond, alkyl, and —CH₂—P¹;P¹ is a phosphorus-containing group of the formula:

R¹ and R² are the same or different and each is selected from H,O-alkyl, O-aryl, alkyl, aryl, and OM,or R¹, R² and the phosphorus atom to which they are bound areencompassed by a ring, for example, R¹ and R² together with a group Yform a group R¹—Y—R², wherein R¹ and R² are the same or different andeach is selected from O-alkyl, O-aryl, alkyl and aryl, and Y is alinking group selected from direct bond, alkylene and —O—, e.g., Y is adirect bond, as in the formula:

R³ is H or alkyl;M=Na, K, Zn, Al, Ca;each a is an integer individually selected from 0 to 4, e.g., 0 1, 2, 3,or 4 provided that at least one a is at least 1;n is an integer from 1 to 100,000, e.g., 2, 3, 4 or 5 to 100,000 and mis an integer from 0 to 100,000, e.g., 1, 2, 3, 4 or 5 to 100,000;andoptionally at least one flame retardant adjuvant material (C).

In one particular embodiment, the organophosphorus compound (B)comprises a unit represented by at least one of the formulas (I), (Ia)or (II) with the proviso that R¹ and R² are not both unsubstitutedphenyl.

It should be understood that in formula (I), (Ia) and (II), where n is2, 3, 4, 5 or higher, each of the individual variables A, R¹, R², R³, Y,M or a for each unit of Formula (I), (Ia) or (II) may be the same ordifferent. For example, a polymer comprising monomer units of Formula(I) can contain monomer units of Formula (I) where the variable ‘a’ is1, and monomer units of Formula (I) where the variable ‘a’ is 0,resulting in a polymer comprising phenyl rings linked by a group A,wherein some of the phenyl rings are substituted by a group (CH₂P¹) andsome of the phenyl rings are not substituted by a group (CH₂P¹).

Conveniently, the organophosphorus compound (B) is present in an amountof about 10% to about 40%, e.g., 10% to about 30%, by weight of theflame-retardant resin composition.

Conveniently, at least one flame retardant adjuvant material (C) ispresent and is selected from melamine, a melamine derivative such as amelamine condensation product or melamine salt, an inorganic metalcompound, a clay material, a layered double hydroxide material, and apolyphenylene ether resin.

Conveniently, the at least one flame retardant adjuvant material (C)comprises a melamine salt and an inorganic metal compound in a weightratio of between about 10:1 and about 1:1 or a condensation product ofmelamine and an inorganic metal compound in a weight ratio of betweenabout 10:1 and about 1:1.

Conveniently, the inorganic metal compound comprises a metal salt suchas a borate, particularly zinc borate.

Conveniently, the melamine salt comprises a melamine phosphate,particularly melamine polyphosphate or melamine pyrophosphate; thecondensation product of melamine conveniently comprises melam, melem ormelon.

Conveniently, the at least one flame retardant adjuvant material (C) ispresent in an amount of about 1 to about 20 wt % of the flame-retardantresin composition. For example, the combination of the organophosphoruscompound (B) and the at least one flame retardant adjuvant material (C)may make up from 11 to 60 wt % of the total composition, e.g., from 11to 50 wt % or from 15 to 40% of the total composition.

Conveniently, the base resin (A) comprises at least one of athermoplastic or thermoset resin. A typical thermoset resin is an epoxyresin and a typical thermoplastic resin is polyester, a polyamide, apolycarbonate or a styrenic resin.

In one embodiment, the base resin (A) comprises a polyamide andparticularly a glass-filled polyamide, typically containing from about15 to about 40% glass by weight of the total weight of the polyamide andglass.

DESCRIPTION OF THE EMBODIMENTS

Described herein is a flame-retardant resin composition comprising abase resin (A), a benzylic-substituted organophosphorus compound (B) andoptionally at least one flame retardant adjuvant material (C).

Base Resin

The base resin can be any organic macromolecular material, such as apolyester-series resin, a styrenic resin, a polyamide-series resin, apolycarbonate-series resin, a vinyl-series resin, an olefinic resin, anacrylic resin, an epoxy resin, a blend of two or more of said resins ora blend of one or more of said resins with a polyphenylene oxide-seriesresin. The base resin can be a thermoplastic or a thermoset resin and insome embodiments further comprise a reinforcing agent, e.g., a glassreinforced resin. Particularly preferred are engineering resins, such aspolyester-series resins, polyamide-series resins and polycarbonates,especially glass-filled polyesters and polyamides.

Polyester-series resins include homopolyesters and copolyesters obtainedby, for example, polycondensation of a dicarboxylic acid component and adiol component, and polycondensation of a hydroxycarboxylic acid or alactone component. Preferred polyester-series resins usually include asaturated polyester-series resin, in particular an aromatic saturatedpolyester-series resin, such as polybutylene terephthalate.

Polyamide-series resins include polyamides derived from a diamine and adicarboxylic acid; polyamides obtained from an aminocarboxylic acid, ifnecessary in combination with a diamine and/or a dicarboxylic acid; andpolyamides derived from a lactam, if necessary in combination with adiamine and/or a dicarboxylic acid. The polyamide also includes acopolyamide derived from at least two different kinds of polyamideconstituent components.

Suitable polyamide-series resins include aliphatic polyamides (such asnylon 46, nylon 6, nylon 66, nylon 610, nylon 612, nylon 11 and nylon12), polyamides obtained from an aromatic dicarboxylic acid (e.g.,terephthalic acid and/or isophthalic acid) and an aliphatic diamine(e.g., hexamethylenediamine, nonamethylenediamine), and polyamidesobtained from both aromatic and aliphatic dicarboxylic acids (e.g., bothterephthalic acid and adipic acid) and an aliphatic diamine (e.g.,hexamethylenediamine), and others. These polyamides may be used singlyor in combination.

The base resin may be composited with a filler to modify its properties,such as mechanical strength, rigidity, thermal stability and electricalconductivity. The filler may be fibrous or non-fibrous. Suitable fibrousfillers include glass fibers, asbestos fibers, carbon fibers, silicafibers, fibrous wollastonite, silica-alumina fibers, zirconia fibers,potassium titanate fibers, metal fibers, and organic fibers having highmelting point (e.g., an aliphatic or aromatic polyamide, an aromaticpolyester, a fluorine-containing resin, an acrylic resin such as apolyacrylonitrile). Suitable non-fibrous fillers include plate-like (orlayered) fillers, such as kaolin, talc, glass flakes, mica, graphite,metal foil, and layered phosphates (e.g., zirconium phosphate, andtitanium phosphate). In addition, particulate or amorphous fillers canbe used including carbon black, white carbon, silicon carbide, silica,powdered quartz, glass beads, glass powder, milled fibers (such asmilled glass fiber), silicates (e.g., calcium silicate, aluminumsilicate, clays, diatomites), metal oxides (e.g., iron oxide, titaniumoxide, zinc oxide, and alumina), metal carbonates (e.g., calciumcarbonate and magnesium carbonate), metal sulfates (e.g., calciumsulfate and barium sulfate), and metal powders.

Preferred fillers include glass fiber and carbon fiber. In oneembodiment, the base resin comprises a glass-filled polyamide containingabout 15 and about 40% glass fiber by weight of the total weight of thepolyamide and glass.

Organophosphorus Compound

The organophosphorus compound employed in the present flame-retardantresin composition can be represented by at least one of the followingformulas (I), (Ia), (II) and (III):

where A is selected from O, S, SO₂, a single bond, alkyl, and —CH₂—P¹;P¹ is a phosphorus-containing group of the formula:

R¹ and R² are the same or different and each is selected from H,O-alkyl, O-aryl, alkyl, aryl, and OM,or R¹, R² and the phosphorus atom to which they are bound areencompassed by a ring, for example, that is, R¹ and R² together with agroup Y form a group R¹—Y—R², which together with the phosphorus atombound to R¹ and R² form a ring:

in whichR¹ and R² are the same or different and each is selected from O-alkyl,O-aryl, alkyl and aryl, andY is a linking group selected from direct bond, alkylene and —O—, e.g.,Y is a direct bond;R³ is H or alkyl;M=Na, K, Zn, Al, Ca;each a is an integer individually selected from 0 to 4, e.g., 0 1, 2, 3,or 4 provided that at least one a is at least 1;n is an integer from 1 to 100,000, e.g., 2, 3, 4 or 5 to 100,000 and mis an integer from 0 to 100,000, e.g., 1, 2, 3, 4 or 5 to 100,000, e.g.,n is an integer from 4 to 100,000, or 5 to 100,000, and m is an integerfrom 1 to 100,000.

In one particular embodiment, the organophosphorus compound (B)comprises a unit represented by at least one of the formulas (I), (Ia)or (II) with the proviso that R¹ and R² are not both unsubstitutedphenyl.

Representative benzylic-substituted organophosphorus compounds withinthe above formulas include diphenylphosphine oxide derivatives ofdiphenyl ether (Compound V below), diphenylphosphine oxide derivativesof diphenoxybenzenes (Compound VI below), diphenylphosphine oxidederivatives of oligomeric aryl ethers (Compound VII below),diphenylphosphine oxide derivative of polyphenylene ethers (CompoundVIII below), diphenylphosphine oxide derivatives of polystyrene(Compound IX below), and p-xylylenebis(diphenylphosphine oxide)(Compound X below) and the corresponding cyclic phosphinates shown:

Conveniently, the organophosphorus compound (B) is present in an amountof about 10% to about 40%, e.g., 10% to about 30%, by weight of theflame-retardant resin composition.

Flame Retardant Adjuvant

To enhance its flame retardant properties, the present resin compositioncan include at least one flame retardant adjuvant material in additionto the organophosphorus compound described above. Suitable flameretardant adjuvant materials comprise melamine and melamine derivativessuch as melamine salts and condensation products of melamine, inorganicmetal compounds, clay compounds, layered double hydroxide materials,polyphenylene ether resins and mixtures thereof.

Suitable melamine salts include salts of melamine itself as well assalts of melamine derivatives, such as substituted melamines (e.g., analkylmelamine such as 2-methylmelamine, guanylmelamine), condensationproducts of melamine (e.g., melam, melem, melon), and copolycondensedresins of melamine (e.g., melamine-formaldehyde resins, phenol-melamineresins, benzoguanamine-melamine resins and aromatic polyamine-melamineresins). Generally the salts are produced by reaction of the melaminewith an oxygen-containing acid, such as nitric acid, a chloric acid(such as perchloric acid, chloric acid, chlorous acid, hypochlorousacid), a phosphorous acid, a sulfuric acid, a sulfonic acid, a boricacid, a chromic acid, an antimonic acid, a molybdic acid, a tungsticacid, stannic acid, or silicic acid.

Examples of suitable melamine salts include melamine orthophosphate,melamine phosphate, melamine pyrophosphates (including melaminepyrophosphate and dimelamine pyrophosphate), melamine polyphosphates(including melamine triphosphate and melamine tetraphosphate), melaminesulfates (including melamine sulfate, dimelamine sulfate andguanylmelamine sulfate), melamine pyrosulfates (e.g., melaminepyrosulfate and dimelamine pyrosulfate), melamine sulfonates (e.g.,melamine methanesulfonate, melam methanesulfonate, and melemmethanesulfonate) and melamine orthoborates (e.g., mono- to trimelamineorthoborates).

The preferred melamine salts are melamine pyrophosphates. Preferredcondensation products of melamine comprise melam, melem or melon.

Suitable inorganic metal compounds for use in the present synergistcombination include metal salts of inorganic acids, metal oxides andhydroxides, and metal sulfides.

Where the inorganic metal compound is a metal salt of an inorganic acid,suitable inorganic acids include phosphorous acids (such asorthophosphoric acid, metaphosphoric acid, phosphorous acid,hypophosphorous acid, hypophosphoric, pyrophosphoric acid,polyphosphoric acids, anhydrous phosphoric acid and polymetaphosphoricacid), boric acids (such as orthoboric acid, metaboric acid; pyroboricacid, tetraboric acid, pentaboric acid and octaboric acid), a stannicacid (such as stannic acid, metastannic acid, orthostannic acid andhexahydroxostannic acid), a molybdic acid, and a tungstic acid.

Examples of suitable metal salts include calcium pyrophosphate, calciumpolymetaphosphate, alkaline earth metal hydrogenphosphates (such asmagnesium hydrogen orthophosphate and calcium hydrogen orthophosphate);transition metal hydrogenphosphate (such as manganese hydrogenphosphate,iron hydrogenphosphate, zinc hydrogenphosphate and cadmiumhydrogenphosphate); a hydrogenphosphate of a metal of Group 13 of thePeriodic Table of Elements (such as aluminum hydrogenphosphate); ahydrogenphosphate of a metal of Group 14 of the Periodic Table ofElements (such as tin hydrogenphosphate), an alkaline earth metal borate(such as calcium orthoborate, calcium metaborate, calcium pyroborate andtrimagnesium tetraborate); a transition metal borate (such as manganeseorthoborate, manganese tetraborate, nickel diborate, copper metaborate,zinc metaborate, zinc tetraborate, cadmium metaborate and cadmiumtetraborate), an alkali metal stannate (e.g., sodium stannate andpotassium stannate), an alkaline earth metal stannate (e.g., magnesiumstannate), a transition metal stannate (e.g., cobalt stannate and zincstannate), zinc molybdate and zinc tungstate.

Examples of suitable metal oxides and hydroxides include molybdenumoxide, tungstic oxide, titanium oxide, zirconium oxide, tin oxide,copper oxide, zinc oxide, aluminum oxide, nickel oxide, iron oxide,manganese oxide, antimony trioxide, antimony tetraoxide, antimonypentoxide, aluminum hydroxide, magnesium hydroxide, tin hydroxide, andzirconium hydroxide. Mixed oxides such as aluminosilicates, includingclays, can also be used.

Examples of suitable metal sulfides include molybdenum sulfide, tungsticsulfide and zinc sulfide. The preferred inorganic metal compounds areborates and particularly zinc borates.

In one embodiment, the flame retardant adjuvant is a combination of amelamine salt and an inorganic metal compound in a weight ratio ofbetween about 10:1 and about 1:1. In another embodiment, the flameretardant adjuvant comprises a combination of a melamine condensationproduct and an inorganic metal compound in a weight ratio of betweenabout 10:1 and about 1:1.

In another embodiment, the flame retardant adjuvant material is achar-forming organic compound such as a polyphenylene ether (PPE) typeresin. A specific PPE resin example would be PPO 803 from SabicInnovative Plastics. The PPE resin can be used typically at a load levelof up to 50%, e.g., between about 1% and about 25%, more typicallybetween about 5% and about 15%.

The invention will now be more particularly described with reference tothe following

EXAMPLES Example 1 Preparation of Diphenylphosphine Oxide Derivative ofDiphenyl Ether

Diphenyl ether (100 g), 50 g of paraformaldehyde, and 400 mL of aceticacid were stirred at 60° C. HCl (304 g) was bubbled through the solutionover 5 hour. After aqueous workup in methylene chloride, andconcentration of the organics, 146.1 g of a clear liquid was obtained.¹H NMR spectrum was consistent with the structure shown and indicatedthe material was predominantly the para isomer. The clear liquid (120g), 356 g of ethyl diphenylphosphinite, and 500 g of dichlorobenzenewere stirred at 165° C. overnight. The product was isolated bycrystallization and repeated digestion/washing to give compound V (137.0g) as a white solid. Analysis: TGA 5% wt loss: 342° C.; 10.3% P; DSC(melt): 274.4, 279.2° C.

Example 2 Preparation of Diphenylphosphine Oxide Derivative ofDiphenoxybenzene

Diphenoxybenzene (100 g), paraformaldehyde (45.6 g), 33% HBr in aceticacid (748 g) and methylene bromide (632 g) were stirred at 60° C. forseveral hours, then 90° C. overnight. After aqueous workup andconcentration, 214.7 g of a thick amber liquid was obtained. The thickamber liquid (210 g), ethyl diphenylphosphinite (439 g), and1,2-dichlorobenzene (2 L) were heated at 160° C. overnight. A Dean-Starktrap was used to remove the volatiles. After cooling to roomtemperature, the reaction material was filtered. The white powderobtained was slurried in hexanes at room temperature and gave 162 g ofmaterial after drying. The white powder product (135 g) was washed withacetone and gave, after filtration and drying, 95.0 g of Compound VI asa solid. Analysis: TGA 5% loss: 290.9° C.; 9.85% P.

Example 3 Preparation of Diphenylphosphine Oxide Derivative ofOligomeric Aryl Ether

Compound 1C was produced using a modification of a procedure describedin German Patent Publication No DE 3,334,068 A1. Poly(phenylene ether)oligomers (90.0 g; n=0-2), 54.95 g paraformaldehyde, 901 g 33% HBr inacetic acid, and 900 g of dibromomethane were heated with stirring for4.5 hour at 60° C. The reaction mixture was then brought to 90° C. andheld at that temperature overnight. The reaction mixture was then washedand the organics were concentrated under vacuum to afford 194.1 g of abrown solid intermediate. Analysis: Organic bromide: 46.78%; ¹H NMR(CDCl3): δ 7.54-6.64 (m); 4.64-4.41 (m).

The brown solid intermediate (186.9 g), 304 g of ethyldiphenylphosphinite, and 3 L of 1,2-dichlorobenzene were heated at 160°C. under a blanket of nitrogen overnight with stirring. The volatileswere removed by use of a Dean-Stark trap. The reaction material wasconcentrated under vacuum. The concentrate (256.6 g) was heated withstirring with 256 g of 1,2-dichlorobenzene and 56 g of ethyldiphenylphosphinite at 175° C. overnight. The reaction mixture was thencooled to room temperature and then reprecipitated with hexanes. Afterfiltration and vacuum drying, 251 g of Compound VII was obtained as awhite solid. Analysis: TGA 5% loss: 314.2° C. 10.26% P; ³¹P NMR (CDCl3):δ −21.70 (m).

Example 4 Preparation of Diphenylphosphine Oxide Derivative ofSubstituted Polyphenylene Ether

A polyphenylene ether resin (PPO 803 resin from GE Plastics) (45 g),22.5 g of paraformaldehyde, 367.4 g of 33% HBr in AcOH, and 150 g ofmethylene bromide were stirred and heated at 60° C. overnight. Afterworkup the organics were precipitated into acetone. Upon drying, 78.9 gof a white powder was obtained. Analysis: ¹H NMR (CDCl3): δ 6.07 (m),4.75 (m), 4.2-1.90 (m). The white powder (70.0 g), 151.3 g of ethyldiphenylphosphinite, and 1,2-dichlorobenzene (2 L) were heated at 160°C. overnight. A Dean-Stark trap was used to remove the volatiles. Thereaction mixture was then concentrated to half volume by distillation.The concentrated reaction mixture was precipitated with acetone and thenreprecipitated. After filtration and drying, Compound VIII, 93.1 g, wasobtained as a white powder. Analysis: TGA 5% loss: 353.1° C.; 8.73% P.

Example 5 Preparation of Diphenylphosphine Oxide Derivative ofPolystyrene

Poly(vinyl benzyl chloride) (77.5 g), 349 g of ethyldiphenylphosphinite, and 430 g of 1,2-dichlorobenzene were heated at160° C. under a blanket of nitrogen overnight with stirring. Thevolatiles were removed by use of a Dean-Stark trap. The reaction mixturewas taken up in 300 mL of methylene chloride and the productprecipitated with of hexanes and then reprecipitated. After washing,filtration, and drying, compound IX was obtained as 138 g of a tanpowder. Analysis: DSC (Tg): 125.7° C.; TGA 5% loss: 350.2° C.; 9.58% P.

Example 6 Preparation of P-Xylylenebis(Diphenylphosphine Oxide)

Compound 3A was produced using a modification of a procedure describedby Bodrin, G. V. et al., Inst. Elementoorg. Soedin. Moscow, USSR.Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya 1979, (11), 2572-5.Ethyl diphenylphosphinite (522 g), 180 g of α,α′-dichloro-p-xylene, and2,400 g of 1,2-dichlorobenzene were stirred with heating at 160° C.under a blanket of nitrogen overnight. The volatiles were removed by useof a Dean-Stark trap. The mixture was then allowed to cool to roomtemperature and was filtered. The resulting wet-cake was washed withhexanes. After filtration and then vacuum drying, Compound X wasobtained as 487 g of a white powder. Analysis: TGA 5% loss: 365° C.;12.0% P.

Example 7 Use of Flame Retardants in Glass-Reinforced PA66

The various flame retardant compounds described in Examples 1 to 6 wereformulated with PA66 resin by mixing the materials either with a twinscrew extruder using a PA66 glass concentrate to produce a target 30%glass fiber reinforcement or in a vented Brabender Preparation Center.In the Brabender Preparation Center the samples were compounded for fourminutes at 265° C. About 3 minutes after the start of mixing, glassfiber was added over a period of about 15 seconds to produce a target30% glass fiber reinforcement. The compounded materials were ground on aThomas Wiley mill and then molded by using a small injection moldingmachine at 265° C. to form 1/16″ thick UL-94 test bars.

The test bars were subjected to the UL-94 vertical burn test protocol inwhich a bar is subjected to two 10 second flame applications. The timefor the bar to extinguish after each application is noted and reportedas Time 1 (T1) and Time 2 (T2) for the bar. The average burn times for 5test bars were noted for both flame applications (T1, T2). The totalburn times were also summed for each of the two flame applicationsacross all five test bars along with the observations of any drippingbehavior. The results are shown in Table 1.

TABLE 1 Formulation 1 2 3 4 5 6 % PA 66 Resin 30.2 50 40 % Zytel 70G43L69.8 70 70 70 Resin(a) % Glass 30 30 Compound V 30 Compound VI 30Compound VIII 30 Compound X 20 30 UL-94 Burn Results Ave. T1/T2, s >30,  3/2(c) 13/3  23/24  20/2  9/2 BD/BTC(c) Total Burn N/A    15/10 64/14113/5  100/8 44/9 Time T1/T2, s Dripping(b) BD/BTC   BD BD BD BD noneRating Fail V-2 V-2 V-2 V-2 V-1 (a)A 43% Glass - PA66 resin concentratefrom DuPont. (b)BD = Burning Drip: Indicates burning material from thebar ignited the cotton. BTC = burned completely to the clamp. (c)UL Teston 1/32″ thick sample bars.

As evidenced in Table 1, the addition of 30% of Compounds V, VI, or VIIIshowed FR properties, giving a V-2 rating. The addition of 20 or 30% ofthe Compound X material also showed flame retardant properties comparedwith the control (formulation 1) by giving either no drips incombination with reduced burn times, or by reducing the burn timesduring the test. Formulation 6 was just shy of reaching a V-0classification.

Example 8 Use of Flame Retardant in Glass-Reinforced PA66 with Melamineor PPE Based Adjuvants

Formulations were made as described in Example 7 and the molded barswere tested for flammability as shown in Table 2. Various melamine basedmaterials were also added to the formulations as FR adjuvant compoundsto determine the effect on flammability properties. A PPE resin was alsotested as an FR adjuvant material in this system. The test bars weresubjected to the UL-94 vertical burn test protocol and the average burntimes for 5 test bars were noted for both flame applications (T1, T2).The total burn times were also summed for each of the two flameapplications across all five test bars along with the observations ofany dripping behavior.

TABLE 2 Formulation 7 8 9 10 11 12 13 % PA 66 Resin 0 37 37 42 45 37 %Zytel 70G43L 70.0 66.6 Resin(a) % Glass 30 30 30 30 30 Compound V 14.2Compound X 17 17 17 17 20 17 PPE(b) 11 MP-200(c) 11 Budit 311(d) 11 1114.2 Budit 3141(d) 0 11 Zinc Borate 2 5 5 5 5 UL-94 Burn Results Ave.T1/T2, s 4.5/1.8 1.2/0.6 1.6/1.0  9/1 17/3  31/5 3.4/4.6 Total Burn Time25 6/3 8/5 47/3 84/10 154/25 17/23 T1/T2, s Dripping(e) none none noneBD BD none BD Rating V-0 V-0 V-0 V-2 V-2 near V-2 V-1 (a)A 43% Glass -PA66 resin concentrate from DuPont. (b)PPE = PPO 803/808 from GEPlastics (Now Sabic Innovative Plastics). (c)MP-200 = Melapur 200.Melamine polyphosphate from Ciba. (d)Budit 3141 = Melamine polyphosphatefrom Budenheim; Budit 311 = Melamine pyrophosphate from Budenheim. (e)BD= Burning Drip: Indicates burning material from the bar ignited thecotton. BTC = burned completely to the clamp.

These formulations show an increase in flame retardancy versus thecontrol formulation 1 (Table 1) and, in most cases, actually gave V-0 FRperformance when used in combination with the melamine based FRadjuvants. Additionally, using an organic-based char-forming FR-Adjuvantlike PPE resin also improved the flame retardancy. In the cases with themelamine compounds, the addition of zinc borate helped to eliminate thedrips and gave a V-0 classification.

Example 9 Use of Flame Retardants in Glass-Reinforced PA66 with Clay/LDHBased FR Adjuvants

Formulations were made as described in Example 7. A clay, Cloisite 30Bfrom Southern Clay Products, was used as an FR adjuvant to determine itseffects on the burn properties. This clay is a quaternary ammonium saltmodified natural montmorillonite material. Additionally a zinc-aluminumZn2Al(OH)6 layered double hydroxide (LDH) material was tested as anadjuvant. The test bars were subjected to the UL-94 vertical burn testprotocol and the average burn times for 5 test bars was noted for bothflame applications (T1, T2). The total burn times were also summed foreach of the two flame applications across all five test bars along withthe observations of any dripping behavior. The results are summarized inTable 3.

TABLE 3 Formulation 14 15 16 17 18 19 20 % PA 66 Resin 65 50 45 35 35 2737 % Glass 30 30 30 30 30 30 30 Compound VII 28 Compound IX 38 CompoundX 15 20 30 30 Clay 5 5 5 5 5 5 LDH 5 UL-94 Burn Results Ave. T1/T2, s109/0 15/4  1/2  1/1 11/5  0.3/0.3  4/1 Total Burn 545/0 75/19 6/11 3/453/25 1/1 19/6 Time T1/T2, s Dripping(a) none none none none none/BDnone none Rating Fail V-1 V-0 V-0 V-2 V-0 V-0 (a)BD = Burning Drip:Indicates burning material from the bar ignited the cotton.

The data in Table 3 clearly shows the FR benefits of using these typesof materials in a resin formulation. Formulation #14, with only clayadded as a control, gave no dripping, but had very long burn times.Addition of various levels of Compound X improved the flame retardantproperties to V-1, and then to V-0 at a higher load level. The use ofother benzylic based polymeric FR materials, Compounds VII and IX, alsoshowed good flame retardant properties, showing the generality of thisapproach. Using LDH instead of the clay showed some dripping behavior,giving a V-2 classification.

Example 10 Use of Flame Retardants in Unreinforced PA66 Formulations

In order to test the effect of the glass fiber reinforcement and todetermine if these materials also exhibit flame retardant properties inthe absence of such reinforcement, formulations were made as describedabove and the molded bars were tested for flammability as shown in Table4. The test bars were subjected to the UL-94 vertical burn test protocoland the average burn times for 5 test bars was noted for both flameapplications (T1, T2). The total burn times were also summed for each ofthe two flame applications across all five test bars along with theobservations of any dripping behavior.

TABLE 4 Formulation 21 22 % PA 66 Resin 65 60 Compound X 30 30 Clay 5 5Zinc Borate 5 UL-94 Burn Results Ave. T1/T2, s 11/6  3/4 Total Burn TimeT1/T2, s 56/28 13/20 Dripping none/none none/none Rating V-1 V-0

The data in Table 4 demonstrates the utility of these materials as flameretardants in unreinforced resins as well. The addition of zinc borateas FR adjuvant further increased the flame retardant properties from V-1to V-0.

Example 11 Preparation of DOPO-Methylene-Poly(Phenylene Ether)

Lithium bis(trimethylsilyl)amide-[LiHMDS] (52 g, 0.31 mol) and THF (220mL) were added to a 1 L round-bottom flask fitted with an over-headstirrer, temperature probe, addition funnel and reflux condenser. Thesolution was placed under N₂, cooled to 5° C. (ice bath) and9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide, i.e., DOPO, (70 g,0.32 mol) was added portion-wise over 10 minutes while maintaining aninternal temperature below 10° C. Upon complete addition,bromo-methylated poly(phenylene ether (44 g, 0.27 mol) (as described inExample 3, but with slightly higher molecular weight) in THF (120 mL)was added via addition funnel over 1 hr. During the addition, theinternal temperature rose to 25° C. and a yellow/white slurry wasobtained. Upon complete addition, the reaction slurry was allowed tostir at room temperature for 16 hours and then concentrated to a solidunder reduced pressure. The resulting yellow solid was taken up inmethylene chloride (300 mL), washed with H₂O, dried, filtered andconcentrated to provide an off white solid. This solid was placed in avacuum oven (210° C., 29 in. Hg) for 3 hours, to provide the titlecompound (87 g) as a glass after cooling to room temperature.

Example 12 Use of Flame Retardants in Glass-Reinforced PA66

Glass-Reinforced PA66 formulations comprising the flame retardant ofExample 11 were compounded and molded as described in Example 7. TheUL-94 Vertical Burn Test results are shown in Table 5. This data showsthat at certain load levels of FR or adjuvant synergist in combination,a strong flame retardant system can be achieved.

TABLE 5 Testing of Compound XI with Melem in 30% GR PA66. Formulations23 24 25 Polyamide 6,6, % 55.2 45.2 42.2 Glass, % 30 30 30 Cmpd XI, %12.4 12.4 15.4 DELACAL NFR HP, % 0 10 10 Drip & Stabilizer Package¹ 2.42.4 2.4 UL-94 VBT ( 1/16″) Ave T1/T2, s 28/— 15/0 2/0 Drips BB/C² NoneNone Tot. Burn Time (5 B), sec. 143 77 11 Rating V-2 V-1 V-0 ¹0.4% PTFE(Dyneon TF 9205); 2% Surlyn ²Burning bar/chunk which separated at theclamp & continued to burn on the chamber floor DELACAL NFR HP is amulti-component material comprised of the two main homologues melem andmelam, available from Delamin, Ltd.

While the present invention has been described and illustrated byreference to particular embodiments, those of ordinary skill in the artwill appreciate that the invention lends itself to variations notnecessarily illustrated herein. For this reason, then, reference shouldbe made solely to the appended claims for purposes of determining thetrue scope of the present invention.

The invention claimed is:
 1. A flame-retardant comprising one or morepolymers comprising a unit represented by formula (I), (Ia) or (II):

where A is selected from O, S, SO₂, a single bond, alkyl, and —CH₂—P¹;P¹ is a phosphorus-containing group of the formula:

wherein R¹ and R² together with a group Y form a group R¹—Y—R², whichtogether with the phosphorus atom bound to R¹ and R² form a ring:

in which R¹ and R² are the same or different and each is selected fromO-alkyl, O-aryl, alkyl and aryl, and Y is a linking group selected fromdirect bond, alkylene and —O—; R³ is H or alkyl; each a is an integerindividually selected from 0 to 4, provided that at least one a is atleast 1; n is an integer from 4 to 100,000, and m is an integer from 0to 100,000.
 2. The flame-retardant according to claim 1 comprising oneor more polymers comprising a unit represented by formula (I), or one ormore polymers comprising a unit represented by formula (II) wherein m isfrom 1 to 100,000.
 3. The flame-retardant according to claim 1 whichcomprises one or more compounds comprising a unit represented by formula(Ia) or (II).
 4. The flame-retardant according to claim 1 comprising oneor more polymers having a formula (VIIa), (VIIb), (VIIIa) or (IXa):


5. The flame-retardant according to claim 4 comprising at least onepolymer of formula (VIIa) or (VIIb).
 6. The flame-retardant according toclaim 4 comprising at least one polymer of formula (Villa).
 7. Theflame-retardant according to claim 4 comprising at least one polymer offormula (IXa).
 8. A flame retardant composition comprising a flameretardant according to claim 1 and a base resin selected from the groupconsisting of polyester resins, styrenic resins, polyamide resins,polycarbonate resins, vinyl resins, olefinic resins, acrylic resins,epoxy resins, blends of two or more of said resins, and blends of one ormore of said resins with a polyphenylene oxide-series resin.
 9. Theflame retardant composition according to claim 8 wherein the base resincomprises a polyamide resin.
 10. The flame retardant compositionaccording to claim 8 wherein the flame retardant is present in an amountof from about 10% to about 40% by weight of the total flame-retardantcomposition.
 11. The flame retardant composition according to claim 8wherein the base resin comprises a polyester resin, styrenic resin,polyamide resin, polycarbonate resin or epoxy resin.
 12. The flameretardant composition according to claim 11 wherein the base resinfurther comprises a glass reinforcing agent.
 13. The flame retardantcomposition according to claim 12 wherein the base resin comprises aglass-filled polyamide resin, comprising from about 15 to about 40%glass by weight of the total weight of the polyamide and glass.
 14. Theflame retardant composition according to claim 8 further comprising atleast one flame retardant adjuvant material selected from melaminecondensation products, melamine salts, inorganic metal compounds, claycompounds, layered double hydroxide materials, and polyphenylene etherresins and mixtures thereof.
 15. The flame retardant compositionaccording to claim 14, wherein the melamine salt comprises a melaminephosphate, polyphosphate, and/or melamine pyrophosphate.
 16. The flameretardant composition according to claim 14, wherein the melaminecondensation product comprises one or more of melam, melem or melon. 17.The flame retardant composition according to claim 14 comprising atleast one melamine salt and/or melamine condensation product and atleast one adjuvant selected from the group consisting of metal oxides,metal hydroxides, clay compounds and layered double hydroxide materials.18. The flame retardant composition according to claim 14, wherein saidat least one flame retardant adjuvant material is present in an amountof about 1 to about 20 wt % of the flame-retardant resin composition.19. The flame retardant composition according to claim 14, wherein theinorganic metal compound is selected from metal salts of inorganicacids, metal oxides and hydroxides, metal sulfides and mixtures thereof.20. The flame retardant composition according to claim 19, wherein theinorganic metal compound comprises a borate.